This application relates generally to techniques for distributing air in an enclosed space, such as a building or a room thereof and, more particularly, to overhead or ceiling-mounted systems.
When air of a temperature different from the ambient temperature is directed, such as by way of a heating, ventilating and air-conditioning (“HVAC”) system, into a confined space (e.g., open refrigeration cases in retail stores) or entryways, air stratification tends to result. In other words, the air in the enclosed space forms temperature layers with the warmer air rising to the ceiling while the cooler area sinks to the floor.
It is known to utilize ceiling fans for moving warm air adjacent to the ceiling downward toward the floor, in an attempt to destratify the air in a building or room. However, such attempts have been unsatisfactory, since the ceiling fans either do not move the air very far or create a drafty condition. Furthermore, they are visible and may be unsightly and/or noisy. Also, they tend to create a diffuse or widely scattered air flow that can upset the air curtain adjacent to open coolers or refrigerated cases.
An attempt has been made to produce a columnar air flow by using a ceiling-mounted fan arrangement which forces air through a conical focusing ring and/or through tapering passages in a grid or a grille, such an arrangement being disclosed, for example, in U.S. Pat. No. 4,730,551. However, that arrangement is relatively complex, utilizing filters and movable grille elements, and has had mixed success in destratifying air.